1. Field of the Invention
The present invention relates to an apparatus for measuring a refracting characteristic of a lens, particularity eyeglass lenses, and more particularly to an apparatus for measuring a lens-refracting characteristic of eyeglasses in positions corresponding to pupils of eyes.
2. Description of Related Art
Generally, when manufacturing eyeglasses, a distance between optical centers of right and left lenses of eyeglasses and a distance between pupils of right and left eyes for a person wearing eyeglasses are set to be equal such that the centers of the pupils coincide with the optical centers of the lenses of eyeglasses for the person wearing the eyeglasses, respectively.
In this case, respective distances from the center of the nose of the person wearing the eyeglasses to the respective centers of pupils of the right and left eyes, namely, half pupillary distances are respectively measured. Accordingly, the right and left half pupillary distances conform to the half optical center distances from the center between the right and left eyeglass lenses to the optical centers of the right and left eyeglass lenses, respectively.
Conventionally, there has been known a lens-refracting characteristic measuring apparatus for measuring an optical center distance between light and left lenses of such eyeglasses (For example, reference to Japanese Patent Laid-Open H08-29292).
However, there may be a case that right and left half pupillary distances of actually manufactured eyeglasses do not agree with the right and left half optical center distances of the eyeglasses. When the centers of pupils for a person wearing eyeglasses do not accurately agree with the centers of the eyeglass lenses, respectively, the person wearing the eyeglasses has to wear the eyeglasses in a state in which prism occurs, in other words, a plurality of refractions are generated. In such eyeglasses, it was impossible to accurately measure the refracting characteristics of the eyeglass lenses in the positions corresponding to the centers of the pupils of the person wearing the eyeglasses.
On the other hand, there may be a case when a person wearing eyeglasses includes heterophoria and cross-eye, amount of prism is set in case of manufacturing the eyeglasses. The optical center distance of the eyeglasses manufactured by the amount of prism does not conform to the above mentioned pupillary distance. When the pupillary distance of such eyeglasses was measured, it was impossible to judge whether the amount of prism is set for the cross eye or not, or whether the half pupillary distances do not agree with the optical center distances or not.
Moreover, when the amount of prism was set for the cross-eye, it was hard to determine whether the amount of prism is appropriately set or not.